1. Field of the Invention
This invention relates to a power output control system for an internal combustion engine including an electric throttle control device for electrically controlling a throttle valve, and more particularly to a power output control system for controlling the power output of the engine when the electric throttle control device is in a condition incapable of controlling the throttle valve.
2. Description of the Prior Art
Conventionally, a power output control system of the above-mentioned kind has been disclosed e.g. in Japanese Laid-Open Patent Publication No. 11-22530. According to the power output control system, when a throttle valve has become uncontrollable e.g. due to an electrical or mechanical failure of an electric throttle control device, the electric throttle control device is deenergized, and at the same time the degree of opening of the throttle valve is held at a default opening degree so as to avoid an engine stall and allow the vehicle to travel to find a nearby place to park.
Further, the power output control system is configured such that when the accelerator pedal is not stepped on at all or completely released, the torque generated by the engine is reduced to an amount corresponding to an idle engine rotational speed by correction of the air-fuel ratio of a mixture and the ignition timing, and when the accelerator pedal is stepped on from the released state, the rotational speed of the engine is increased to thereby prevent degradation of drivability.
As described above, according to this power output control system, when the throttle valve becomes uncontrollable due to failure of the electric throttle control device, if the accelerator pedal has been stepped on, i.e. the vehicle is actually traveling to find a nearby place to park (hereinafter, this travel carried out in case of uncontrollability of the throttle valve will be referred to as xe2x80x9crefuge runningxe2x80x9d), the degree of opening of the throttle valve is held in the default opening degree which makes the rotational speed of the engine slightly higher than the idle engine rotational speed. Therefore, it is impossible to secure a sufficient amount of intake air when the vehicle is performing refuge running, and although the refuge running is possible, the vehicle cannot attain adequate traveling performance.
It is an object of the invention to provide a power output control system for an internal combustion engine, which enables the vehicle to smoothly perform refuge running while ensuring adequate traveling performance, when an electric throttle control device becomes incapable of controlling a throttle valve.
To attain the above object, according to a first aspect of the present invention, there is provided a power output control system for an internal combustion engine including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to the engine, and an accelerator pedal,
the power output control system comprising:
uncontrollability-determining means for determining whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve;
energization-interrupting means for interrupting energization of the electric throttle control device when it is determined by the uncontrollability-determining means that the electric throttle control device is in the condition incapable of controlling the throttle valve;
default opening-holding means for holding a degree of opening of the throttle valve at a default opening degree when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve;
rotational speed-detecting means for detecting a rotational speed of the engine;
load-detecting means for detecting load on the engine;
basic ignition timing-calculating means for calculating basic ignition timing according to the rotational speed detected by the rotational speed-detecting means and the load on the engine detected by the load-detecting means;
accelerator pedal operation amount-detecting means for detecting an amount of operation of the accelerator pedal; and
ignition timing-determining means for determining ignition timing of the engine by correcting the basic ignition timing according to the detected amount of operation of the accelerator pedal when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to this power output control system, when it is determined that the electric throttle control device is incapable of controlling the throttle valve, first, energization of the electric throttle control device is interrupted to stop control of the throttle valve by the electric throttle control device. At the same time, the degree of opening of the throttle valve is held at the default opening degree by the default opening-holding means to supply intake air in an amount enabling the vehicle to perform refuge running, i.e. to find a nearby place to park. Further, ignition timing of the engine is determined by the ignition timing-determining means by correcting basic ignition timing calculated based on the rotational speed of the engine and load on the same by the basic ignition timing-calculating means, according to the accelerator pedal opening.
Therefore, when the electric throttle control device is determined to be incapable of controlling the throttle valve, the basic ignition timing is corrected according to the amount of operation of the throttle valve to thereby determine the ignition timing. This makes it possible to obtain the power output of the engine according to the amount of operation of the throttle valve, i.e. driver""s demand, which enables the vehicle to smoothly perform the refuge running. As a result, the default opening degree of the throttle valve can be configured to be larger than in the case of the conventional power output control system, thereby ensuring adequate traveling performance of the vehicle during the refuge running.
Preferably, the ignition timing-determining means determines the ignition timing by correcting the basic ignition timing such that the ignition timing is retarded by a largest amount when the amount of operation of the accelerator pedal is equal to or smaller than a predetermined value, and as the amount of operation of the accelerator pedal becomes larger than the predetermined value, the ignition timing becomes closer to the basic ignition timing.
To attain the above object, according to a second aspect of the invention, there is provided a power output control system for an internal combustion engine including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to the engine, and an accelerator pedal,
the power output control system comprising:
an uncontrollability-determining module for determining whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve;
an energization-interrupting module for interrupting energization of the electric throttle control device when it is determined by the uncontrollability-determining module that the electric throttle control device is in the condition incapable of controlling the throttle valve;
a default opening-holding module for holding a degree of opening of the throttle valve at a default opening degree when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve;
a rotational speed-detecting module for detecting a rotational speed of the engine;
a load-detecting module for detecting load on the engine;
a basic ignition timing-calculating module for calculating basic ignition timing according to the rotational speed detected by the rotational speed-detecting module and the load on the engine detected by the load-detecting means;
an accelerator pedal operation amount-detecting module for detecting an amount of operation of the accelerator pedal; and
an ignition timing-determining module for determining ignition timing of the engine by correcting the basic ignition timing according to the detected amount of operation of the accelerator pedal when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to the second aspect of the invention, the same advantageous effects as provided by the first aspect of the invention can be obtained.
Preferably, the ignition timing-determining module determines the ignition timing by correcting the basic ignition timing such that the ignition timing is retarded by a largest amount when the amount of operation of the accelerator pedal is equal to or smaller than a predetermined value, and as the amount of operation of the accelerator pedal becomes larger than the predetermined value, the ignition timing becomes closer to the basic ignition timing.
To attain the above object, according to a third aspect of the invention, there is provided a power output control method for controlling power output of an internal combustion engine including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to the engine, and an accelerator pedal,
the power output control method comprising the steps of:
determining whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve;
interrupting energization of the electric throttle control device when it is determined that the electric throttle control device is in the condition incapable of controlling the throttle valve;
holding a degree of opening of the throttle valve at a default opening degree when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve;
detecting a rotational speed of the engine;
detecting load on the engine;
calculating basic ignition timing according to the detected rotational speed and the detected load on the engine;
detecting an amount of operation of the accelerator pedal; and
determining ignition timing of the engine by correcting the basic ignition timing according to the detected amount of operation of the accelerator pedal when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to the third aspect of the invention, the same advantageous effects as provided by the first aspect of the invention can be obtained.
Preferably, the step of determining the ignition timing includes correcting the basic ignition timing such that the ignition timing is retarded by a largest amount when the amount of operation of the accelerator pedal is equal to or smaller than a predetermined value, and as the amount of operation of the accelerator pedal becomes larger than the predetermined value, the ignition timing becomes closer to the basic ignition timing.
To attain the above object, according to a fourth aspect of the invention, there is provided an engine control unit including a control program for causing a computer to control power output of an internal combustion engine including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to the engine, and an acceleration pedal,
wherein the control program causes the computer to determine whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve, interrupt energization of the electric throttle control device when it is determined that the electric throttle control device is in the condition incapable of controlling the throttle valve, hold a degree of opening of the throttle valve at a default opening degree when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve, detect a rotational speed of the engine, detect load on the engine, calculate basic ignition timing according to the detected rotational speed and the detected load on the engine, detect an amount of operation of the accelerator pedal, and determine ignition timing of the engine by correcting the basic ignition timing according to the detected amount of operation of the accelerator pedal when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to the fourth aspect of the invention, the same advantageous effects as provided by the first aspect of the invention can be obtained.
Preferably, when the program causes the computer to correct the basic ignition timing such that the ignition timing is retarded by a largest amount when the amount of operation of the accelerator pedal is equal to or smaller than a predetermined value, and as the amount of operation of the accelerator pedal becomes larger than the predetermined value, the ignition timing becomes closer to the basic ignition timing.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.